The present invention generally relates to sand processing apparatus, and more particularly to apparatus for blending or mixing water with sand.
Process sand is used in a variety of applications. In foundries, for example, process sand is prepared for use as molds and cores to produce castings from molten metal. The sand is mixed with bentonite, and other ingredients are typically added to the sand so that it maintains a formed shape. Molten metal is poured into the molds and allowed to cool, thereby forming a solid casting. A shake-out process is used to remove the sand from the casting. The shake-out process is typically conducted at relatively high temperatures so that the binder added to the sand is pyrolyzed.
In order to reduce sand consumption, it is common for foundries to include sand reconditioning apparatus which allows the sand to be reused in subsequent molds. Because the sand has a relatively high temperature as it exits the shake-out, it is common for the reconditioning apparatus to add water to the sand to reduce the temperature of the sand. The temperature of the sand is most quickly and efficiently reduced when the water is thoroughly mixed throughout the sand. Accordingly, conventional apparatus typically includes a generally horizontal conveyor belt on which the sand is carried. One or more nozzles are positioned above the conveyor belt for spraying water onto a top surface of the sand. In addition, a mixing device is often located above a portion of the conveyor belt downstream of the water nozzles for blending the water with the sand.
Conventional mixing devices typically include a plurality of rotating paddles or blades which are positioned to engage the sand on top of the conveyor belt. As the blades rotate, the water applied to the top surface of the sand is dispersed throughout a majority of the sand. It will be appreciated, however, that the blades must be positioned so that the range of motion of the blades does not interfere with the conveyor belt, and therefore a lower layer portion of the sand will remain unmixed. In addition, since the mixing device is positioned above the conveyor belt, the blades are in contact with each section of the sand stream for only a limited amount of time as the sand is transported past the blades.
A conventionally known alternative to the rotating blades is the use of a pair of counter-rotating augers positioned below the conveyor belt. While the augers may have an increased longitudinal length to increase the amount of mixing time, the amount of mixing is still limited primarily by the speed of the augers and volume within the mixing vessel. A further drawback of such conventional mixing devices is that they are located in-line with the main sand processing flow. As a result, if the mixing device fails, the entire sand process is halted.
After the water has been added to the sand, the water and sand mixture is typically fed into cooling apparatus. Most types of cooling apparatus include a housing which is maintained at a controlled temperature. One of the more common methods of maintaining the temperature inside the enclosure is by providing air. The temperature of the air used in the cooling apparatus is controlled so that the air itself has a known enthalpy. In addition, the moisture content of the sand entering the cooling apparatus may be measured and the air temperature selected so that the sand exiting the cooling apparatus has a desired moisture content.
Upon exiting the cooling apparatus, the sand is generally suitable for remixing and further use as molds or cores. It is possible, however, that additional moisture must be added in order to activate bentonite or other materials in the sand.
In accordance with certain aspects of the present invention, apparatus for mixing water into a stream of sand is provided, the apparatus comprising a conveyor for transporting the sand stream, the conveyor having a loading end and a discharge end. A receptacle has an inlet positioned below the conveyor discharge end and an outlet, a vertical path being defined between the conveyor discharge end and the receptacle inlet. A first mixer has a rotatable shaft extending at least partially into the receptacle, and an agitator is attached to and rotates with the shaft inside the receptacle. Opposed first and second nozzle sets are provided which are adapted for attachment to a water source, each nozzle set comprising at least one nozzle directed at the vertical flow path for spraying water toward the vertical flow path. The nozzles coat opposing surfaces of the sand stream with water as the sand falls along the vertical flow path and the rotating agitator mixes the sand and water inside the receptacle.
In accordance with additional aspects of the present invention, a method of blending water with sand is provided, the method comprising the step of creating a vertical stream of sand having front and rear faces. Water is sprayed onto the front and rear faces of the sand stream to create a wetted sand stream. The wetted sand stream is collected in a receptacle and mixed to obtain a thorough mixture of sand and water.
In accordance with still further aspects of the present invention, apparatus for mixing water into a stream of sand is provided, the apparatus comprising a conveyor for transporting the sand stream, the conveyor having a loading end and a discharge end. A receptacle has an inlet positioned below the conveyor discharge end and an outlet, a vertical path being defined between the conveyor discharge end and the receptacle inlet. A first mixer has a rotatable shaft extending at least partially into the receptacle, and an agitator is attached to and rotates with the shaft inside the receptacle. A second mixer has a rotatable shaft extending at least partially into the receptacle, and an agitator is attached to and rotates with the shaft inside the receptacle. A motor drives the shafts of the first and second mixers in opposite directions. Opposed first and second nozzle sets are adapted for attachment to a water source, each nozzle set comprising at least one nozzle directed at the vertical flow path for spraying water toward the vertical flow path. The nozzles coat opposing surfaces of the sand stream with water as the sand falls along the vertical flow path and the rotating agitator mixes the sand and water inside the receptacle.